That is pretty slick! And I'm glad to see someone else putting a lot of ingenuity into using a kettle for more than grilling hamburgers!
Although I don't consider it smoking, I always refer to it as smoke/roasting. In my case, I've always done it indirect and recently using bricks to shore up the coals on one side. 2 bricks made a world of difference as they act as a heat sink and keep temps more consistent.
The thing with the way you did it is that you have more room using the middle of the grate. ON the down side, the pan has direct heat under it and like you found out, any liquid in the pan will cook down pretty fast. Even using a drip pan under mine, next to the coals, I have to watch to make sure it doesn't get the pan to hot.
It's amazing though, you can just about leave them alone over night once you get the right set up. It's good to have the Maverick to alert you if it gets out of the zone, but as you proved, the kettles can hold good constant temps!
BTW, that piggy looked incredible! If it was a little dry, you can use a little finishing sauce (NC style) tossed in for moisture, and the subtle vinegar makes a world of difference on pork too!
Congrats!!
PS. I the idea of the baking stone is a good one. We have an old one I've planned on trying to figure a way to use in my WSM too. Also bricks turns up sideways with the holes horizontal. It's too much fun tinkering with these things.